Add PSRAM support to ESP32S2

[tannewt]

When configured the CircuitPython heap will be on the external RAM.
When not available, the heap will be 48k inside the IDF heap.

[ladyada]

hi want me to test on hardware?

[tannewt]

If you like. I tested on WROVER and FeatherS2 on stream.

[ladyada]

ok this loaded onto my saola but i cant seem to get displayio demo on oled running

import board
import busio
import displayio
import adafruit_displayio_ssd1306
displayio.release_displays()

print(dir(board))
i2c = busio.I2C(board.IO8, board.IO9)
display_bus = displayio.I2CDisplay(i2c, device_address=0x3d)
display = adafruit_displayio_ssd1306.SSD1306(display_bus, width=128, height=64)

->

13:31:29.471 -> �[0;32mI (862) cpu_start: Starting scheduler on PRO CPU.�[0m
13:31:42.631 -> Guru Meditation Error: Core  0 panic'ed (LoadProhibited). Exception was unhandled.
13:31:42.631 -> 
13:31:42.631 -> Core  0 register dump:
13:31:42.631 -> PC      : 0x400aa917  PS      : 0x00060e30  A0      : 0x800b0ddb  A1      : 0x3ffce390  
13:31:42.631 -> A2      : 0x00000000  A3      : 0x00000000  A4      : 0x00000000  A5      : 0x3ffce180  
13:31:42.631 -> A6      : 0x3ff7fc70  A7      : 0x00000001  A8      : 0x800a9e39  A9      : 0x3ffce370  
13:31:42.631 -> A10     : 0x3f00f0ec  A11     : 0x00000000  A12     : 0x3ffcae70  A13     : 0xffffff30  
13:31:42.677 -> A14     : 0x3ffc624c  A15     : 0x00000004  SAR     : 0x00000018  EXCCAUSE: 0x0000001c  
13:31:42.677 -> EXCVADDR: 0x00000004  LBEG    : 0x3ffcae70  LEND    : 0xffffff30  LCOUNT  : 0x40029051  
13:31:42.677 -> 
13:31:42.677 -> Backtrace:0x400aa914:0x3ffce390 0x400b0dd8:0x3ffce3b0 0x400b1e75:0x3ffce3d0 0x400ad213:0x3ffce3f0 0x40091836:0x3ffce410 0x4008d795:0x3ffce430 0x4008d895:0x3ffce450 0x4009abf2:0x3ffce470 0x400918e6:0x3ffce510 0x4008d795:0x3ffce540 0x4008d7c2:0x3ffce560 0x400a747b:0x3ffce580 0x400a77ba:0x3ffce630 0x4009d859:0x3ffce650 0x4009d922:0x3ffce680 0x4009dbcb:0x3ffce6d0 0x4009dd9b:0x3ffce6f0 0x400b7609:0x3ffce710 0x4002dea9:0x3ffce740
13:31:42.724 -> 
13:31:42.724 -> 
13:31:42.724 -> ELF file SHA256: 3b524f297f3f1a35
13:31:42.724 -> 
13:31:42.724 -> CPU halted.

i dont know if its related - this is my first time in a long time trying out circuitpy on esp32s!

[hierophect]

I'll try a control from main today. That error indicates some kind of invalid memory access, but not a null dereference as per EXCVADDR being nonzero.

[tannewt]

@ladyada What module does your Saola have? Does it have PSRAM? I suspect your issue may not be related to this PR.

[microdev1]

I tested PSRAM support on microS2 and it works. 👍

[jerryneedell]

Works on my saola_wrover

Press any key to enter the REPL. Use CTRL-D to reload.
Adafruit CircuitPython 6.0.0-alpha.2-358-gf39708abb on 2020-08-26; Saola 1 w/Wrover with ESP32S2
>>> import gc
>>> gc.mem_free()
2048784
>>> ```

[hierophect]

I can confirm a null reference exception when attempting to use DisplayIO on the Saola Wrover. Investigating.

[hierophect]

@ladyada @tannewt I've confirmed that the issue with DisplayIO also happens on main and thus is probably unrelated to this PSRAM update. I've opened a new issue for it here: #3334. @ladyada if you'd like to keep testing this PR, I think most other sketches should still work, you just got unlucky with the one you tried landing on a new bug! It only occurs when the screen is physically plugged in, so removing it should allow you to recover your filesystem.

[dhalbert]

Should I wait for this for 6.0.0-alpha.3?

[tannewt]

@dhalbert Want to approve? Seems like it's ready to go in.

[dhalbert]

Looks good, and has been confirmed as working. Thanks!